The severity of a concussion generally depends on the severity of the blow to the head, but exactly how hard of a collision is needed to cause even minor damage to neurological development? Research supported by the National Institutes of Health (NIC) and the National Operating Committee on Standards for Athletic Equipment (NOCSAE) found that even the slightest traumatic brain injury (TBI) can cause damage to brain tissue that controls the speed of nerve signals, also known as white matter

"We found differences in the white matter of the brain in these college contact sport athletes compared to non-contact sport varsity athletes," said study author Dr. Thomas W. McAllister of Indiana University School of Medicine in Indianapolis. "This group of athletes with different susceptibility to repetitive head impacts raises the question of what underlying factors might account for the changes in learning and memory, and whether those effects are long-term or short-lived."

Dr. McAllister and his colleagues recruited 80 varsity football and ice hockey players from Dartmouth College’s Division I athletic program who had not suffered a concussion. Each athlete’s cognitive abilities were assessed using brain scans in addition to learning and memory tests. The research team fitted each player with a state-of-the-art helmet that records the head’s acceleration-time following a collision. Data from 80 concussion-free Division I football and ice hockey players was compared against 79 athletes from non-contact sports including track, crew, and Nordic skiing.

In both contact and non-contact sport athletes, a subgroup of participants that scored lower than researchers expected on verbal learning and memory tests was identified. Around 20 percent of athletes competing in contact sports and 11 percent of non-contact athletes experienced a change in nerves that connect the right side of the brain to the left, the corpus callosum region. Dr. McAllister said this alteration of the brain’s makeup occurs in less than seven percent of non-athletes.

"The degree of white matter change in the contact sport athletes was greater in those who performed more poorly than expected on tests of memory and learning, suggesting a possible link in some athletes between how hard/often they are hit, white matter changes, and cognition, or memory and thinking abilities," Dr. McAlister added.

According to the American Academy of Neurology, a concussion is a type of traumatic brain injury resulting from a bump on the head violent enough to jolt the brain’s movement within the skull. Identifying the possible severity of a concussion relies on symptoms including confusion, memory loss, mood swings, nausea, headaches, light sensitivity, and trouble sleeping. Along with the cognitive impairment of learning and memory, a concussion can also double a person’s risk of developing epilepsy within five years of suffering a traumatic brain injury.

Approximately 173,285 sports-related traumatic brain injuries are treated at emergency departments around the U.S. each year. The majority of sports-related traumatic brain injuries among boys are associated with football (55,007) while TBI’s suffered by girls are connected to soccer. Out of 173,285 sports-related TBI’s each year, 70.5 percent of TBI emergency room visits are attributed to people between the ages of 10 and 19.